Device intended for measuring a dose of powdered medicament for inhalation

ABSTRACT

The invention relates to a device intended for measuring a dose of powdered medicament for inhalation, including a medicament container (1), through which extends a shaft (3) provided with at least one dosage recess (5). Container (1) is provided with at least one flap-like sweeper element (4), resting on shaft (3) in alignment with the dosage recess and having one of its ends rotatable around shaft (3), the other end of said flap dragging along the shaft surface, whereafter said shaft (3) is displaceable in this longitudinal direction relative to container (1) so as to bring dosage recess (5), along with a dose of the medicament carried therein, outside container (1). The invention relates also to the measuring of a dose of powdered medicament for inhalation by using the device described above.

The present invention relates to a section of a powder inhalatorrequired for the inhalation of a powdered medicament, said sectioncontaining powdered medicament as well as a mechanism required formeasuring its dosage and delivering it out of a reservoir.

The dosage of a medicament for inhalation is generally effected by usinga propellant-pressurized dosage aerosol or powder inhalator. With dosageaerosol, the metering of a dose is accurate based on the determinationof liquid volume in a dosage valve with external moisture having noeffect on the procedure. With powder inhalators, the metering isinaccurate for several reasons. Measuring or metering a dose is based ontwo prior known principles. The powder may be contained as measuredportions in small dosage containers, e.g. capsules, from which it ismetered and delivered into the inhalation air of a patient. A largeramount of powdered medicament can also be contained in a reservoirincluded in an inhalator, wherein a special mechanism is used fordelivering a measured amount of powder into the inhalation air of apatient. Such multi-dosage inhalators are more convenient to a patientby virtue of their easy operation.

The medicament doses to be inhaled with powder inhalators may varywithin the range of tenths of a milligram to tens of milligrams. Thesmaller the doses in question, the more difficult it is to effect asufficiently accurate measuring of the dose and the greater adetrimental effect of extraneous disturbing factors on measuringaccuracy. The most significant disturbing factor is external moisture .If a powdered medicament is moistened, e.g. during storage, it may formlumps for impaired measuring accuracy. The penetrability of moistureinto a medicinal substance depends on the tightness of a medicamentreservoir, the water-vapour permeability of a structural material aswell as on the moisture absorbency of a medicament itself. It is priorknown to alleviate the moisture trouble by means of a dehydrating agentassociated with a medicament reservoir.

Moisture has also another effect on the accuracy of a medicament dosedischarging from an inhalator. If those internal surfaces of aninhalator, which are in contact with discharging medicament powder,become moist, the delivered amount of medicament will be reduced to afraction of the normal. The moistening may be a result of exhalationthrough an inhalator or of bringing the device from a cold place to awarm one. This moisture trouble could be inhibited by fitting theinhalator with a one-way valve preventing exhalation and other air-flowsoccurring through the device.

On the basis of what is stated above, a medicament reservoir and a dosemeasuring mechanism included in a multi-dosage inhalator should fulfilthe following conditions:

to measure at a sufficient accuracy both large and small doses

have a structure as tight and compact as possible

in terms of its structure, to facilitate the use of a one-way valve inthe inhalator.

Further, in terms of total medication costs, it would be preferable touse a replaceable medicament reservoir.

Thus, with multi-dosage powder inhalators, the design of a medicamentreservoir and a dose measuring mechanism is highly important not only interms of dose measuring accuracy and stability of a powdered medicamentbut also a preferred inhalator structure. No prior art multidosagepowder inhalator is provided with a medicament reservoir and a dosemeasuring mechanism that would fulfil all the above-mentionedconditions.

Finnish Patent publication No. 69963 discloses a multidosage dispenserprovided with a medicament container and a dose metering device. Themedicament container has a conical lower section and its bottom isprovided with a shaft rotatable around its longitudinal axis. The shaftis fitted with one or a plurality of dosage recesses, into which thepowder is flowing upon rotating said shaft. The container can be fittedwith a dehydrating agent and a vibrator for an intensified flow of thepowder upon rotating said shaft. After rotating the shaft through half aturn, the dosage recess has rotated so as to reach an inhalationconduit, which is located below the container and into which the powderdrops.

The powdered medicament is well protected against moisture but it isrequired to have exceptionally good flowing or trickling properties fora uniform filling of the dosage recess. When using a design as describedabove, it is possible for a patient to receive an overdose of medicamentif several loading actions are effected prior to inhalation. Themedicament container is not replaceable, nor is there provided a one-wayvalve for blocking exhalation.

U.S. Pat. No. 4 046 146 discloses a multi-dosage inhalator, wherein thedose metering is effected by rotating a cylindrical medicament containerhaving a perforated floor. The cylinder rotates around its center axisupon a fixed, circular bottom plate provided with a hole for dropping adose into an inhalation conduit. As the medicament container is rotated,the holes in its floor are filled with a powdered medicament and wind upbelow a plate inside the container in alignment with a hole in thecircular bottom plate, wherethrough the powder falls downgravitationally for inhalation.

The powdered medicament is poorly protected against moisture due to anextensive, untight sliding surface and a hazard of overdoses is ominousif several loading actions are effected prior to inhalation. Measuringof small doses is obviously inaccurate since gravity alone is notsufficient to cause a complete drop of the dose into an inhalationconduit. The design does not allow for effective use of a one-way valve.However, the medicament container is replaceable.

Finnish Patent publication No. 79947 discloses a multi-dosage inhalator,wherein the powder is packed in a medicament reservoir on a perforatedsheeting and the perforated point of the sheeting is carried onto aninhalation conduit. In a commercially available device as set forth inthis patent, the sheeting comprises a thin, circular plastic disc which,upon effecting a loading action, rotates into an inhalation conduit. Themedicament reservoir is provided with a dehydrating agent. Despite thedehydrant, moisture will be able to affect the powdered medicament intime by way of wide and extensive sliding surfaces. The action of thisdevice is troubled by a hazard of blocking the holes of a perforatedplate and the sticking of medicament to the moist interior walls of aninhalation conduit. The medicament reservoir is not replaceable. Themechanism can be used to measure both small and large amounts ofmedicament.

In the present invention, the question is about a medicament containerand a dose measuring mechanism for a multi-dosage powder inhalator formeasuring or metering accurately both large and small medicament doseswith the powdered medicament permanently and tightly protected fromexternal moisture and for readily facilitating the use of a one-wayvalve for blocking exhalation through the powder inhalator as well asreplaceability.

Operation of the device is based on filling a recess in across-sectionally circular shaft with an amount equivalent of a singledose of powdered medicament by rotating a shaft-surrounding medicamentcontainer around the shaft and in an inhalation conduit adjacent to thedose by pushing the shaft out of the medicament container. Filling ofthe recess is effected as a result of the gravity-induced powder rollingand by means of a sweeper element, fastened to the medicament containerand leaning against the shaft. The sliding surfaces between shaft andmedicament container are elastically tight.

A device of the invention is characterized in that the container isprovided with at least one flap-shaped sweeper element, which rests uponthe shaft in alignment with a dosage recess and one of whose ends isrotatable around the shaft, the other end of said flap dragging alongthe shaft surface, whereafter the shaft is displaceable in itslongitudinal direction relative to the container so as to bring thedosage recess along with a medicament dose contained therein to aposition below the container.

The invention will now be described in more detail with reference madeto the accompanying drawings, in which

FIG. 1 is a basic view of a device of the invention with a medicamentcontainer sectioned in the longitudinal direction of the shaft,

FIGS. 2 a, b and c show the device of FIG. 1 in the longitudinaldirection of the shaft, wherein the container is turned through a fullrotation,

FIGS. 3 a and b illustrate one embodiment according to the invention,

FIGS. 4 a and b show an inhalation apparatus including a device of theinvention,

FIG. 5 illustrates another inhalation apparatus provided with a deviceof the invention, and

FIGS. 6-9 show one modified embodiment of FIG. 5.

Referring to FIG. 1, the basic structure of a device is shown with amedicament container sectioned in the longitudinal direction of a shaft3 and FIG. 2 shows it in a cross-section in the direction of the shaft.The device comprises a medicament container housing 1, a gable 2, acircular shaft 3 as well as a flap-shaped sweeper element 4 leaningagainst the shaft with a slight tension. In alignment with sweeperelement 4, said shaft 3 is provided with a recess 5 for measuring adose. A powdered medicament 6 lies freely on the floor of medicamentcontainer 1. Inside the container it is possible to place a dehydratingagent 7, packed e.g. as an annular body. Shaft apertures 8 are tight butallow for displacement of the shaft in its longitudinal direction. Ifnecessary, there may be a plurality of dosage recesses 5 and those canbe located in various parts of shaft 3. The number of sweeper elements 4can also be more than one. The medicament container 1 has preferably acircular cross-section but other shapes are also possible. The shaft 3is preferably located centrally in the medicament container but can alsobe located eccentrically.

A dose measuring or metering procedure is illustrated in FIGS. 2a, b andc. Upon rotating the medicament container, the powdered medicament first(FIG. 2a) rotates along with the container but, upon continued rotation,it starts to trickle and fall downwards ending up on sweeper element 4(FIG. 2b). As one rotation is completed, the sweeper element 4 haspacked said dosage recess 5 full of powder with a slight tension (FIG.2c). By pushing shaft 3 the dose can be displaced out of the containerand simultaneously the tight shaft aperture 8 trims out a possibleexcess powder. As a strong gas flow (e.g. induced by inhalation) isdirected to dosage recess 5, the latter is exhausted of the powderedmedicament. The term "recess" refers to a depression, located in theshaft and having a volume that matches an individual dose of medicament.

Tests have verified that a device provided with a single dosage recess 5and sweeper element 4 is capable of reaching a measuring accuracy ofappr. ±10% when measuring doses of more than 2 mg. In this case, themedicament container 1 can be half-filled with powder and the measuringaccuracy begins to deteriorate after appr. 2/3 of the powder has beenspent. Hence, a cylindrical medicament container 1, having a diameter of2 cm and a height of 1 cm, is capable of measuring or metering more than200 doses of 2 mg (depending on the specific gravity of a powder inquestion). Tests have also verified that the flowing characteristics ofcertain medicinal formulations are insufficient for an accurateoperation of the device. This calls for the use of a mechanism which, ina per se known manner, vibrates the medicament container duringrotation. The flowing and the filling of a dosage recess can also beintensified by a special design of the interior container wall as wellas by adjusting the length and width of a sweeper element and by aneccentric positioning of shaft 5. When measuring doses of less than 2mg, it is preferable to employ a shaft design as shown in FIG. 3,wherein the shaft 3 is hollow at one end slightly beyond said dosagerecess 5. Inside the shaft 3 is fitted a stationary tube 9. After dosagerecess 5 has been filled, said shaft 3 is pushed out of container 1while tube 9 retains its position (FIG. 3b). As some of the gas flow(e.g. induced by inhalation) is directed to pass through said tube 9,the dosage recess is effectively exhausted of medicament.

The medicament container 1 and the gable with its sweeper element 4 fora device of the invention can be readily manufactured from plastics andthe components can be joined together e.g. by press-fitting orultrasonic welding. If the employed material comprises a suitablyelastic material, e.g. soft polyethylene or rather stiff elastomer, noseparate shaft sealings 8 are not required. A preferred material for theshaft and its inner tube is polished stainless steel.

The filling of a medicinal substance in the container can be effectedprior to the attachment of a gable to the container, as one of its shaftapertures is closed, or respectively through the other shaft aperturewith the gable in position.

A device of the invention can be replaced in the housing of a powderinhalator either without or with a shaft. If a replacement is effectedwithout a shaft, the shaft apertures of a medicament container areprotected for the duration of storage by means of a plug, extendingthrough the medicament container and having one of its ends providedwith a depression for receiving the shaft end. After removing an emptycontainer from the shaft, the shaft end is placed in this depression andthe container is pushed onto the shaft, which forces the plug in frontit out of the container. The container will be installed in its properposition according to alignment marks carried therein as well as in theinhalator housing.

A device of the invention is capable of measuring at a sufficientaccuracy both very small and large amounts of powder. The powderedmedicament is extremely well protected from moisture and its designreadily facilitates the use of a one-way valve for blocking exhalationthrough the device. It is easy to manufacture and its replaceabilityguarantees reasonable maintenance costs.

The following description deals with examples for assembling a device ofthe invention to serve as a complete powder inhalator.

FIG. 4a illustrates a simple device, wherein the passage of a dose intoan inhalation conduit 10 is effected by manually pressing a button 11.The shaft comprises a massive shaft as shown in FIG. 1, one of its endsleaning against a socket 13 tensioned by a spring 12. The medicamentcontainer is tensioned in its position by means of an annular,spring-equipped gear- mechanism 14, which only allows the rotation ofthe medicament container in a proper direction and also vibrates themedicament container upon the rotation thereof for a smoother flow ofpowdered medicament. The shaft is chamfered at 15 in order to maintainits proper position. The example discloses the use of a digital dosecounter 16 as well as a contact 17. The container is replaceable byunlocking a clamp unit 18, whereby a section including the containerdisenegages together with its shaft along a line 19 (FIG. 4b) and themore expensive section, including the dose counter, is in permanentservice.

When using the device, a medicament container 1 is manually turnedthrough one rotation e.g. according to alignment marks, which isfollowed by pressing in a button 11 and by inhaling through a mouthpiece20. Upon releasing, the button returns to its original position, wherebythe dosage recess pushes itself inside the medicament container is readyfor use again.

FIG. 5 illustrates a more complicated embodiment, wherein a device ofthe invention is used for measuring relatively small amounts of powderin association with a vortex chamber pulverizing pharmaceuticalparticles, as disclosed in Finnish Patent application 892956. The deviceemploys a shaft design as illustrated in FIG. 3. The passage of a doseoccurs automatically out of the medicament container and the inhalatoris well protected against moistening caused by exhalation.

The medicament container has a front cover 2, adapted to serve as therear wall of a vortex chamber 21. The other gable of the container isprovided with two meshings, one 22 being in contact with a gear 24 andthe other 23 with a spring 25 mounted on the inhalator housing, thepurpose of said spring being to prevent rotation of the container in awrong direction as well as to vibrate the container during rotation. Ashaft 26 carries a reversing wheel 27, a splined cylinder 28 as well asa gear 24 and terminates in a prod 29 for supplying an impulse to adigital dose counter 16. A shaft 3 is fitted with a transfer means 30,one of its ends communicating by way of journalled wheels nearlynon-frictionally with the slot of splined cylinder 28 as well as with arail located below the transfer means and in the bottom section of theinhalator.

When reversing wheel 27 is turned through one rotation, said shaft 3advances into medicament container 1, said inner tube 9 closes the floorof dosage recess 5, the dosage recess fills up, and shaft 3 passes toits original position out of medicament container 1 into said vortexchamber 21. During inhalation through mouthpiece 20, a flap valve 32serving as a one-way valve opens and air flows through a vortex-chamberinlet tube 33 into the chamber. A small portion of inhalation airtravels through dosage recess 5 along tube 9 for thoroughly removing,together with the intra-chamber vortex, the medicament from the dosagerecess.

Exhalation through the device can be done through the dosage recess andtube 9. In practice, however, this is not possible since, when measuringor metering small doses, the hole in the floor of a dosage recess isless than 1 mm in diameter and, thus, a patient does not feel capable ofexhaling with a flap valve closing the actual air inlet.

If a massive shaft is employed, exhalation through the device iscompletely blocked.

The medicament container is replaced by unlocking a hinged portionincluded in clamp unit 18 and by turning reversing wheel 27 through onerotation. Thus, medicament container 1 comes out as pushed by the shaft,whereby it is easy to pull off of shaft 3. A fresh container isinstalled in position, as described above (page 9).

FIGS. 6-9 illustrate one modification to FIG. 5 of an inhalation deviceprovided with a novel metering system. In this modification of aninhalation device, a shaft 3 equipped with a dosage recess 5 remainsstationary but, instead, a medicament container 1 and its associatedvortex chamber 21 along with its nozzle 20 are movable. A separatesection including medicament container 1 is disposed around a fixedshaft 3 provided with dosage recess 5, said shaft penetrating throughthe medicament container. The open end of the medicament container isprovided with a vortex chamber 1 along with its nozzle. A portion ofmedicament container 1 is provided along its outer wall with aprojecting stud, fitting in a spiral slot included in the device. Whenthe device is rotated, the stud travelling in the spiral slot of themedicament container forces medicament container 1 along with its vortexchamber outwards, whereby said medicament container 1 moves and rotatesrelative to shaft 3. The slot configuration is selected to obtain acomplete reciprocating action over a single rotation. In FIG. 6, thedevice is illustrated in a closed inhalation position, wherein theinhalation recess 5 of shaft 3 is located in vortex chamber 21. In FIG.7, the device is illustrated at the half-way point of a loading action,wherein said medicament container 1 has displaced outwards relative toshaft 3 in a manner that said dosage recess 5 is now located inmedicament container 1. FIG. 8 shows a cross-section along a line A--Ain FIG. 6 and FIG. 9 illustrates the device in an opened condition forthe replacement of a container for a medicinal substance 1.

I claim:
 1. A device intended for measuring a dose of powderedmedicament for inhalation, comprising a medicament container (1),through which extends a shaft (3) provided with at least one dosagerecess (5), characterized in that said container (1) is provided with atleast one flap-shaped sweeper element (4) having opposite ends, restingon shaft (3) in alignment with the dosage recess and having one of itsends rotatable around said shaft (3), the other end of the flap draggingalong the shaft surface, said shaft (3) being displaceable in itslongitudinal direction relative to said container (1) so as to bringsaid dosage recess (5) along with its dose of medicament outside saidcontainer (1).
 2. A device as set forth in claim 1, characterized inthat one of the ends of sweeper element (4) is fastened to the wall ofcontainer (1), said container being rotatable around shaft (3).
 3. Adevice as set forth in claim 1 or 2, characterized in that said shaft(3) is at least partially hollow.
 4. A device as set forth in claim 3,characterized in that said dosage recess (5) is in communication withthe hollow section of shaft (3).
 5. A device as set forth in claim 3,characterized in that the wall of shaft (3) is provided with a recess(5) opening into the hollow space and that the hollow space includes astationary tube (9), which extends into medicament container (1) to theproximity of its other wall past recess (5), said shaft (3) beingpushable relative to the container and said fixed tube (9) through sucha distance that said recess (5) is brought outside container (1).
 6. Adevice as claimed in claim 1, characterized in that said medicamentcontainer (1), together with its flap-shaped sweeper element (4) andlead-in sealings (8), is replaceable.
 7. A device as claimed in claim 1,characterized in that the device is provided with a limiter for thedirection of container rotation, said limiter preventing the rotation ofcontainer (1) in a wrong direction.
 8. An inhalation apparatus, providedwith a device as claimed in claim 1 intended for measuring a dose ofpowdered medicament for inhalation.
 9. An inhalation apparatus as setforth in claim 8, characterized in that it is provided with a one-wayvalve (32) for preventing exhalation through the apparatus.